Cutting elements having accelerated leaching rates and methods of making the same

ABSTRACT

Cutting elements having accelerated leaching rates and methods of making the same are disclosed herein. In one embodiment, a method of forming a cutting element includes assembling a reaction cell having diamond particles, a non-catalyst material, a catalyst material, and a substrate within a refractory metal container, where the non-catalyst material is generally immiscible in the catalyst material at a sintering temperature and pressure. The method also includes subjecting the reaction cell and its contents to a high pressure high temperature sintering process to form a polycrystalline diamond body that is attached to the substrate. The method further includes contacting at least a portion of the polycrystalline diamond body with a leaching agent to remove catalyst material and non-catalyst material from the diamond body, where a leaching rate of the catalyst material and the non-catalyst material exceeds a conventional leaching rate profile by at least about 30%.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY

The present disclosure relates generally to cutting elements made fromsuperhard abrasive materials and, more particularly, to cutting elementsmade from polycrystalline diamond having a non-catalyst materialaddition that accelerates leaching rates, and methods of making thesame.

BACKGROUND

Polycrystalline diamond (“PCD”) compacts are used in a variety ofmechanical applications, for example in material removal operations, asbearing surfaces, and in wire-draw operations. PCD compacts are oftenused in the petroleum industry in the removal of material in downholedrilling. The PCD compacts are formed as cutting elements, a number ofwhich are attached to drill bits, for example, roller-cone drill bitsand fixed-cutting element drill bits.

PCD cutting elements typically include a superabrasive diamond layer,referred to as a polycrystalline diamond body that is attached to asubstrate. The polycrystalline diamond body may be formed in a highpressure high temperature (HPHT) process, in which diamond grains areheld at pressures and temperatures at which the diamond particles bondto one another.

As is conventionally known, the diamond particles are introduced to theHPHT process in the presence of a catalyst material that, when subjectedto the conditions of the HPHT process, promotes formation ofinter-diamond bonds. The catalyst material may be introduced to thediamond particles in a variety of ways, for example, the catalystmaterial may be embedded in a support substrate such as a cementedtungsten carbide substrate having cobalt. The catalyst material mayinfiltrate the diamond particles from the support substrate. Followingthe HPHT process, the diamond particles may be sintered to one anotherand attached to the support substrate.

While the catalyst material promotes formation of the inter-diamondbonds during the HPHT process, the presence of the catalyst material inthe sintered diamond body after the completion of the HPHT process mayalso reduce the stability of the polycrystalline diamond body atelevated temperatures. Some of the diamond grains may undergo aback-conversion to a softer non-diamond form of carbon (for example,graphite or amorphous carbon) at elevated temperatures. Further,mismatch of the coefficients of thermal expansion between diamond andthe catalyst may induce stress into the diamond lattice causingmicrocracks in the diamond body. Back-conversion of diamond and stressinduced by the mismatch of coefficients of thermal expansion maycontribute to a decrease in the toughness, abrasion resistance, and/orthermal stability of the PCD cutting elements during operation.

It is conventionally known to at least partially remove catalystmaterial from the PCD by introducing at least a portion of the PCD to aleaching agent. However, the rate of the reaction to remove the catalystmaterial from the PCD may be slow, increasing the time of production ofthe PCD cutting elements and, therefore, the costs associated withmanufacturing.

Accordingly, polycrystalline diamond cutting elements that haveaccelerated leaching of catalyst from the polycrystalline diamond bodymay be desired.

SUMMARY

In one embodiment, a method of forming a cutting element includesassembling a reaction cell having a plurality of diamond particles, anon-catalyst material, a catalyst material, and a substrate within arefractory metal container, where the non-catalyst material is generallyimmiscible in the catalyst material when both are held at the greater ofthe melting or liquidus temperature of the catalyst material or thenon-catalyst material. The method also includes subjecting the reactioncell and its contents to a high pressure high temperature sinteringprocess in which the catalyst material promotes formation ofinter-diamond bonding between adjacent diamond particles to form apolycrystalline diamond body that is attached to the substrate. Themethod further includes contacting at least a portion of thepolycrystalline diamond body with a leaching agent to remove catalystmaterial and non-catalyst material from the diamond body, where aleaching rate of the catalyst material and the non-catalyst materialexceeds a conventional leaching rate profile by at least about 30%.

In another embodiment, a cutting element includes a substrate having ametal carbide and a catalyst material, and a polycrystalline diamondbody bonded to the substrate. The polycrystalline diamond body includesa plurality of diamond grains that are bonded to adjacent diamond grainsin diamond-to-diamond bonds and a plurality of interstitial regionspositioned between adjacent diamond grains, where the plurality ofinterstitial regions include a non-catalyst material, the catalystmaterial, the metal carbide, or combinations thereof. A metal carbideconcentration within the diamond body is less than about 70% of aconventional metal carbide concentration.

In yet another embodiment, a drill bit includes a bit body having aleading end structure for drilling a subterranean formation and aplurality of cutting elements mounted to the blades. At least one of theplurality of cutting elements includes a substrate having a metalcarbide and a catalyst material and a polycrystalline diamond bodybonded to the substrate. The polycrystalline diamond body having aplurality of diamond grains bonded to adjacent diamond grains indiamond-to-diamond bonds. The polycrystalline diamond body furtherincludes a plurality of interstitial regions positioned between adjacentdiamond grains, the plurality of interstitial regions having anon-catalyst material, catalyst material, metal carbide, or combinationsthereof. A metal carbide concentration within the diamond body is lessthan about 70% of a conventional metal carbide concentration.

In yet another embodiment, a method of forming a cutting elementincludes assembling a reaction cell having a plurality of diamondparticles, a non-catalyst material, a catalyst material, and a substratewithin a refractory metal container, where the non-catalyst material isgenerally immiscible in the catalyst material when both are held at thegreater of the melting or liquidus temperature of the catalyst materialor the non-catalyst material. The method further includes subjecting thereaction cell and its contents to a high pressure high temperaturesintering process in which the catalyst material promotes formation ofinter-diamond bonding between adjacent diamond particles to form apolycrystalline diamond body that is attached to the substrate. Themethod also includes contacting at least a portion of thepolycrystalline diamond body with a leaching agent to remove catalystmaterial and non-catalyst material from the diamond body, where thenon-catalyst material has a higher rate of reaction with the leachingagent than the catalyst material.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe embodiments, will be better understood when read in conjunction withthe appended drawings. It should be understood that the embodimentsdepicted are not limited to the precise arrangements andinstrumentalities shown.

FIG. 1 is a schematic side cross-sectional view of a PCD cutting elementaccording to one or more embodiments shown or described herein;

FIG. 2 is a detailed schematic side cross-sectional view of the PCDcutting element of FIG. 1A shown at location A;

FIG. 3 is a schematic flow chart depicting a manufacturing process of aPCD cutting element according to one or more embodiments shown ordescribed herein;

FIG. 4 is a schematic flow chart depicting a manufacturing process of aPCD cutting element according to one or more embodiments shown ordescribed herein;

FIG. 5 is a schematic perspective view of a drill bit having a pluralityof PCD cutting elements according to one or more embodiments shown ordescribed herein; and

FIG. 6 is a plot of data depicting weight loss of a PCD cutting elementin a leaching process according to one or more embodiments shown ordescribed herein.

DETAILED DESCRIPTION

The present disclosure is directed to polycrystalline diamond cuttingelements, drill bits incorporating the same, and methods of making thesame. A cutting element made according to the present disclosure may beformed by introducing a non-catalyst material and a catalyst material toa plurality of unbonded diamond particles. The non-catalyst material andthe catalyst material may be generally immiscible with one another whenboth are held at the greater of the melting or liquidus temperature ofthe non-catalyst material or the catalyst material. The components aresubjected to a high pressure high temperature sintering process in whichthe catalyst material promotes formation of inter-diamond bondingbetween adjacent diamond particles to form a polycrystalline diamondbody. The polycrystalline diamond body is further contact with aleaching agent that removes catalyst material and non-catalyst materialfrom the polycrystalline diamond body. The leaching rate of the catalystmaterial and the non-catalyst material exceeds a conventional leachingrate profile of a conventional cutting element made with equivalentdiamond particle size, catalyst concentration, substrate chemistry, andsintering parameters by at least about 30%. Polycrystalline diamondcutting elements having accelerated leaching rates, rotary drill bitsincorporating the same, and methods of making the same are described ingreater detail below.

It is to be understood that this disclosure is not limited to theparticular methodologies, systems and materials described, as these mayvary. It is also to be understood that the terminology used in thedescription is for the purpose of describing the particular versions orembodiments only, and is not intended to limit the scope. For example,as used herein, the singular forms “a,” “an,” and “the” include pluralreferences unless the context clearly dictates otherwise. In addition,the word “comprising” as used herein is intended to mean “including butnot limited to.” Unless defined otherwise, all technical and scientificterms used herein have the same meanings as commonly understood by oneof ordinary skill in the art.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as size, weight, reaction conditions and soforth used in the specification and claims are to the understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties sought to be obtained by theend user. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

As used herein, the term “about” means plus or minus 10% of the value ofthe number with which it is being used. Therefore, “about 40” means inthe range of 36-44.

As used herein, the term “non-catalyst material” refers to an additivethat is introduced to the polycrystalline diamond body, and that is notcatalytic with carbon in forming diamond and inter-diamond grain bonds.

Polycrystalline diamond compacts (or “PCD compacts”, as used hereafter)may represent a volume of crystalline diamond grains with embeddedforeign material filling the inter-granular spaces. In one example, aPCD compact includes a plurality of crystalline diamond grains that arebonded to each other by strong inter-diamond bonds and forming a rigidpolycrystalline diamond body, and the inter-granular regions, disposedbetween the bonded grains and filled with a non-diamond material (e.g.,a catalyst material such as cobalt or its alloys), which was used topromote diamond bonding during fabrication of the PCD compact. Suitablemetal solvent catalysts may include the metal in Group VIII of thePeriodic table. Polycrystalline diamond cutting elements (or “PCDcutting element”, as is used hereafter) include the above mentionedpolycrystalline diamond body attached to a suitable support substrate(for example, cemented tungsten carbide-cobalt (WC—Co)). The attachmentbetween the polycrystalline diamond body and the substrate may be madeby virtue of the presence of a catalyst, for example cobalt metal. Inanother embodiment, the polycrystalline diamond body may be attached tothe support substrate by brazing. In another embodiment, a PCD compactincludes a plurality of crystalline diamond grains that are stronglybonded to each other by a hard amorphous carbon material, for examplea-C or t-C carbon. In another embodiment, a PCD compact includes aplurality of crystalline diamond grains, which are not bonded to eachother, but instead are bound together by foreign bonding materials suchas borides, nitrides, or carbides, for example, bonded by SiC.

As used herein, “conventional cutting elements,” “conventional leachingrate profile,” “conventional metal carbide concentration,” and“conventional dispersive x-ray fluorescence spectrum” refer to cuttingelements or properties of cutting elements made according to comparableprocesses to the newly-disclosed embodiments discussed herein. Suchconventional cutting elements may serve as comparison to thenewly-disclosed embodiments of the present disclosure to demonstratemodifications introduced by the newly disclosed embodiments. Suchconventional cutting elements may exhibit equivalent diamond particlesize distributions, HPHT processing parameters (for example, maximumtemperature, time above sintering temperature, and maximum pressure),and substrate chemistry as comparable newly-disclosed embodiments.

As discussed above, conventional PCD cutting elements are used in avariety of industries and applications in material removal operations.PCD cutting elements are typically used in non-ferrous metal removaloperations and in downhole drilling operations in the petroleumindustry. Conventional PCD cutting elements exhibit high toughness,strength, and abrasion resistance because of the inter-granularinter-diamond bonding of the diamond grains that make up thepolycrystalline diamond bodies of the PCD cutting elements. Theinter-diamond bonding of the diamond grains of the polycrystallinediamond body are promoted during an HPHT process by a catalyst material.However, at elevated temperature, the catalyst material and itsbyproducts that remain present in the polycrystalline diamond body afterthe HPHT process may promote back-conversion of diamond to non-diamondcarbon forms and may induce stress into the diamond lattice due to themismatch in the coefficient of thermal expansion of the materials.

It is conventionally known to remove or deplete portions of the catalystmaterial to improve the thermal stability of the polycrystalline diamondbody. The most common method of removing the catalyst material is aleaching process in which the PCD compact is introduced to a leachingagent, for example, an aqueous acid solution at elevated temperature.The leaching agent may be selected from a variety ofconventionally-known compositions in which the catalyst material isknown to dissolve. By dissolving and removing at least a portion of thecatalyst material from the PCD compact, the abrasion resistance of thePCD compact may be increased due to the reduction in back-conversionrate of the diamond in the polycrystalline diamond body to non-diamondcarbon forms and the reduction in materials having mismatchedcoefficients of thermal expansion. However, a portion of catalystmaterial may still remain in the diamond body of the PCD compact thathave been subjected to the leaching process. The interstitial regionsbetween diamond grains may form “trapped” or “entrained” volumes intowhich the leaching agent has limited or no accessibility. Therefore,these trapped volumes remain populated with the constituents of the PCDformation process. The trapped volumes that contain catalyst materialcontribute to the degradation of the abrasion resistance of the PCDcutting element at elevated temperature that is generated during use ofthe PCD cutting element to remove material. Thus, reduction of trappedcatalyst material may improve the abrasion resistance of PCD compactcutting elements.

The present disclosure is directed to polycrystalline diamond cuttingelements that incorporate a non-catalyst material that is distributedthroughout the polycrystalline diamond body. The non-catalyst materialmay be selected from a variety of materials, including metals, metalalloys, metalloids, metal-organic composites, semiconductors, lowmelting temperature metal oxides, glass, and combinations thereof. Inparticular examples, the non-catalyst material may be lead or bismuth.The non-catalyst material may be introduced to the diamond particlesprior to or concurrently with the HPHT process. The non-catalystmaterial may be distributed throughout the polycrystalline diamond bodyevenly or unevenly, as well as by forming a distribution pattern. Thenon-catalyst material may reduce the amount of catalyst material that ispresent in the polycrystalline diamond body following the HPHT process.Further, the non-catalyst material may reduce the amount of catalystmaterial that is present in the polycrystalline diamond body following acatalyst depletion process or leaching process in which both thenon-catalyst material and the catalyst material are removed from theportions of the polycrystalline diamond body or from the entirepolycrystalline diamond body. Additionally, the non-catalyst materialmay increase the removal rate (or the “leaching rate”) of the catalystmaterial from the polycrystalline diamond body.

Because of the reduction of the catalyst material in the polycrystallinediamond body, polycrystalline diamond cutting elements according to thepresent disclosure exhibit performance that exceeds that of conventionalPCD cutting elements in at least one of toughness, strength, andabrasion resistance.

Referring now to FIGS. 1 and 2, a PCD cutting element 100 is depicted.The PCD cutting element 100 includes a support substrate 110 and apolycrystalline diamond body 120 that is attached to the supportsubstrate 110. The polycrystalline diamond body 120 includes a pluralityof diamond grains 122 that are bonded to one another, including beingbonded to one another through inter-diamond bonding. The bonded diamondgrains 122 form a diamond lattice that extends along the polycrystallinediamond body 120. The diamond body 120 also includes a plurality ofinterstitial regions 124 between the diamond grains. The interstitialregions 124 represent a space between the diamond grains. In at leastsome of the interstitial regions 124, a non-carbon material is present.In some of the interstitial regions 124, a non-catalyst material ispresent. In other interstitial regions 124, catalyst material ispresent. In yet other interstitial regions 124, both non-catalystmaterial and catalyst material are present. In yet other interstitialregions 124, at least one of catalyst material, non-catalyst material,swept material of the support substrate 110, for example, cementedtungsten carbide, and reaction by-products of the HPHT process arepresent. Non-carbon, non-catalyst or catalyst materials may be bonded todiamond grains. Alternatively, non-carbon, non-catalyst or catalystmaterials may be not bonded to diamond grains.

The catalyst material may be a metallic catalyst, including metalliccatalysts selected from Group VIII of the periodic table, for example,cobalt, nickel, iron, or alloys thereof. The catalyst material may bepresent in a greater concentration in the support substrate 110 than inthe polycrystalline diamond body 120, and may promote attachment of thesupport substrate 110 to the polycrystalline diamond body 120 in theHPHT process, as will be discussed below. The polycrystalline diamondbody 120 may include an attachment region 128 that is rich in catalystmaterial promotes bonding between the polycrystalline diamond body 120and the support substrate 110. In other embodiments, the concentrationof the catalyst material may be greater in the polycrystalline diamondbody 120 than in the support substrate 110. In yet other embodiments,the catalyst material may differ from the catalyst of the supportsubstrate 110. The catalyst material may be a metallic catalystreaction-byproduct, for example catalyst-carbon, catalyst-tungsten,catalyst-chromium, or other catalyst compounds, which also may havelower catalytic activity towards diamond than a metallic catalyst.

The non-catalyst material may be selected from a variety of materialsthat are non-catalyst with the carbon-diamond conversion and include,for example, metals, metal alloys, metalloids, semiconductors, andcombinations thereof. The non-catalyst material may be selected from oneof copper, silver, gold, aluminum, silicon, gallium, lead, tin, bismuth,indium, thallium, tellurium, antimony, polonium, lithium, magnesium, andalloys thereof. Following the HPHT process, the non-catalyst materialmay be present in elemental or alloyed form, or in carbides, nitrides,or carbonitrides thereof. In some embodiments, the non-catalyst materialmay be generally immiscible with the catalyst material when both areliquid such that the non-catalyst material and the catalyst material donot significantly alloy with one another when both are liquid. In someembodiments, the non-catalyst material may have a lower liquidus ormelting temperature than the liquidus or melting temperature of thecatalyst material.

Both non-catalyst material and catalyst material may be present in adetectable amount in the polycrystalline diamond body of the PCD cuttingelement both before and after subjecting the polycrystalline diamondbody to leaching. Presence of such materials may be identified by X-rayfluorescence, for example using a XRF analyzer available from BrukerAXS, Inc. of Madison, Wis., USA. Presence of such material may also beidentified using X-ray diffraction, energy dispersive spectroscopy, orother suitable techniques.

The non-catalyst material may be introduced to the unbonded diamondparticles prior to the HPHT process that bonds the diamonds particles inan amount that is in a range from about 0.1 vol. % to about 5 vol. % ofthe diamond body 120, for example an amount that is in a range fromabout 0.2 vol. % to about 4 vol. % of the diamond body 120, for examplean amount that is in a range from about 0.5 vol. % to about 3 vol. %. Inan exemplary embodiment, non-catalyst material may be introduced to theunbonded diamond in an amount from about 0.33 to about 1.5 vol. %.Following this HPHT process and leaching, the non-catalyst materialcontent in the leached region of the diamond body 120 is reduced by atleast about 50%, including being reduced in a range from about 50% toabout 80%.

In the HPHT process that bonds the diamond particles, catalyst materialmay be introduced to the diamond powders. The catalyst material may bepresent in an amount that is in a range from about 0.1 vol. % to about30 vol. % of the diamond body 120, for example an amount that is in arange from about 0.3 vol. % to about 10 vol. % of the diamond body 120,including being an amount of about 5 vol. % of the diamond body 120. Inan exemplary embodiment, catalyst material may be introduced to theunbonded diamond is an amount from about 4.5 vol. % to about 6 vol. %.Following this HPHT process and leaching, the catalyst material contentin the leached region of the diamond body 120 is reduced by at leastabout 50%, including being reduced in a range from about 50% to about90%.

The non-catalyst material and the catalyst material may be non-uniformlydistributed in the bulk of the polycrystalline diamond cutting element100 such that the respective concentrations of non-catalyst material andcatalyst material vary at different positions within the polycrystallinediamond body 120. In one embodiment the non-catalyst material may bearranged to have a concentration gradient that is evaluated along alongitudinal axis 102 of the polycrystalline diamond cutting element100. The concentration of the non-catalyst material may be higher atpositions evaluated distally from the substrate 110 than at positionsevaluated proximally to the substrate 110. In opposite, theconcentration of the catalyst material may be greater at positionsevaluated proximally to the substrate 110 that at positions evaluateddistally from the substrate 110. In yet another embodiment, theconcentrations of the non-catalyst material and the catalyst materialmay undergo a step change when evaluated in a longitudinal axis 192 ofthe polycrystalline diamond cutting element 100. In yet anotherembodiment, the concentrations of the non-catalyst material and thecatalyst material may exhibit a variety of patterns or configurations.Independent of the concentration of the non-catalyst material and thecatalyst material in the polycrystalline diamond body 120, however, bothnon-catalyst material and catalyst material may be detectible alongsurfaces proximately and distally located relative to the substrate 110.

The concentration gradient of the non-catalyst material and the catalystmaterial may affect the overall leaching rate of the polycrystallinediamond body 120, because the catalyst material and the non-catalystmaterial may have different rates of reaction with the leaching agent.For example, the non-catalyst material may exhibit a faster rate ofreaction with the leaching agent than the catalyst material. The regionsof the polycrystalline diamond body 120 that have higher concentrationsof non-catalyst material relative to catalyst material may exhibitincreased leaching rates than regions of the polycrystalline diamondbody 120 that have lower concentrations of non-catalyst materialrelative to catalyst material. Therefore, regions having relatively highconcentrations of non-catalyst material may exhibit particularly fastleaching rates. The leaching rate may decrease as the leaching agentcomes into contact with material in the interstitial regions of thepolycrystalline diamond body 120 having higher concentrations ofcatalyst material.

The gradient of concentration of catalyst material and non-catalystmaterial may further affect the pattern of leaching within thepolycrystalline diamond body 120, for example the pattern of leachingwhen evaluated along the outer diameter of the cutting element 100 whenthe concentration gradient of non-catalyst material and catalystmaterial is arranged along the longitudinal axis of the cutting element100. In such cutting elements 100 that are subjected to the leachingprocess, leaching agent may remove material from the interstitialregions to a greater depth at axial positions of higher non-catalystconcentration and material to a smaller depth at axial positions oflower non-catalyst concentration. Therefore, cutting elements 100 mayexhibit variation in the interface region between leached regions andunleached regions for cutting elements 100 that are less than fullyleached.

In another embodiment, the polycrystalline diamond body 120 may exhibitrelatively high amounts of the catalyst material at positions proximateto the substrate 110 and at which the catalyst material forms a bondbetween the polycrystalline diamond body 120 and the substrate 110. Insome embodiments, at positions outside of such an attachment zone, thenon-catalyst material and the catalyst material maintain theconcentration variation described above.

PCD cutting elements 100 according to the present disclosure may exhibitimproved performance as compared to conventionally produced PCD cuttingelements when evaluated in terms of abrasion resistance and/ortoughness. The performance of PCD cutting elements 100 according to thepresent disclosure may particularly exhibit improved performance whensubjected to conditions of elevated temperature. Such conditions mayoccur when the PCD cutting elements 100 are used in aggressive materialremoval operations, for example, aggressive downhole drilling operationsin the petroleum industry. Performance of the PCD cutting element 100with respect to abrasion resistance may be quantified in laboratorytesting, for example using a simulated cutting operation in which thePCD cutting element 100 is used to machine an analogous material thatreplicates an end user application.

In one example used to replicate a downhole drilling application, thePCD cutting element 100 is held in a vertical turret lathe (“VTL”) tomachine granite. Parameters of the VTL test may be varied to replicatedesired test conditions. In one example, the cutting element that issubjected to the VTL test is water cooled. In one example, the PCDcutting element 100 was positioned to maintain a depth of cut of about0.017 in/pass at a cross-feed rate of about 0.17 in/revolution and acutting element velocity of 122 surface feet per minute. The VTL testintroduces a wear scar into the PCD cutting element 100 along theposition of contact between the PCD cutting element 100 and the granite.The size of the wear scar is compared to the material removed from thegranite to evaluate the abrasion resistance of the PCD cutting element100. The life of the PCD cutting element 100 may be calculated based onthe material removed from the granite as compared to the size of thewear scar abrades through the polycrystalline diamond body 120 and intothe support substrate 110.

In another example, the PCD cutting element 100 is subjected to a dryinterrupted milling test that implements a fly cutting tool holder andworkpiece arrangement in which the PCD cutting element 100 isperiodically removes material from a workpiece and then is brought outof contact with the workpiece. The interrupted milling test is describedin U.S. patent application Ser. No. 13/791,277, the entire disclosure ofwhich is hereby incorporated by reference. The interrupted milling testmay evaluate thermal resistance of the PCD cutting element 100.

In some embodiments, PCD cutting elements 100 according to the presentdisclosure exhibit increased abrasion resistance as compared toconventionally produced PCD cutting elements. In some embodiments, PCDcutting elements 100 according to the present disclosure may exhibit atleast about 30% less wear with an equivalent amount of material removedfrom the granite as compared to conventionally produced PCD cuttingelements, including exhibiting about 78% less wear than a conventionalcutting element, including exhibiting about 90% less wear than aconventional cutting element. In some embodiments, the PCD cuttingelements 100 according to the present disclosure may exhibit at leastabout 30% more material removal from the workpiece as evaluated at theend of life of the PCD cutting element as compared to a conventional PCDcutting element.

PCD cutting elements 100 according to the present disclosure exhibit alower concentration of trapped catalyst material in interstitial regionsbetween the bonded diamond grains as compared to conventionallyprocessed cutting elements. As discussed above, because the trappedcatalyst material that is positioned within the interstitial regions maycontribute to back-conversion of the diamond grains to non-diamond formsof carbon. The propensity of the polycrystalline diamond body 120 of thePCD cutting element 100 to back-convert to non-diamond forms of carbonmay be correlated to the high-temperature abrasion resistance of the PCDcutting element 100. Reducing the amount of the trapped catalystmaterial within the interstitial regions between diamond grains of thepolycrystalline diamond body 120 may reduce the rate of back-conversionof the PCD cutting element 100. Further, reducing the amount of trappedcatalyst material within the interstitial regions between diamond grainsof the polycrystalline diamond body 120 may reduce stress that isinduced into the diamond lattice caused by a mismatch in the thermalexpansion and the modulus of the diamond grains and the catalystmaterial. Therefore, the reduction in the trapped catalyst materialwithin the interstitial regions between the diamond grains resultingfrom the introduction of non-catalyst material into the polycrystallinediamond body 120, improves performance of the PCD cutting element 100 ascompared to conventionally produced PCD cutting elements.

Still referring to FIG. 1, some embodiments of the PCD cutting element100 include a crown portion 402 that is positioned within thepolycrystalline diamond body 120 and along a surface opposite thesubstrate 110. The crown portion 402 is made from a material that isdissimilar from the material of the polycrystalline diamond body 120 andthe support substrate 110. The crown portion 402 may extend into thediamond body 120 from the top surface of the PCD cutting element 100.The crown portion 402 may extend to a depth that is less than about 1 mmfrom the support substrate 110 including being about 300 μm from thesupport substrate 110. The crown portion 402 may limit the depth thatthe catalyst material 94 sweeps into the polycrystalline diamond body120 from the second support substrate 110 during the second HPHTprocess. The crown portion 402 may provide locally modified materialproperties of the PCD cutting element 100. In one embodiment, the crownportion 402 may include, in addition to the bonded diamond grains, acarbide forming material such as, for example and without limitation,aluminum, silicon, titanium, and alloys, carbides, nitrides, orcarbonitrides thereof. In one embodiment, the crown portion 402 mayinclude, in addition to the bonded diamond grains, non-catalyst materialin detectable amounts. Examples of such non-catalyst materials include,for example and without limitation, copper, silver, gold, aluminum,silicon, gallium, lead, tin, bismuth, indium, thallium, tellurium,antimony, polonium, lithium, magnesium and alloys, nitrides, carbides,or carbonitides thereof.

In some embodiments, the polycrystalline diamond body 120 may be free ofsuch materials outside of the attachment region 128.

PDC cutting elements according to the present disclosure may befabricated using so-called “single press” or “double press” HPHTprocess. In a single press HPHT process, diamond particles may besubjected to a high pressure high temperature sintering process in whichdiamond particles are subjected to elevated pressure to form anunbounded diamond volume having a plurality of diamond particles thatcontact one another and a plurality of interstitial regions positionedbetween adjacent diamond particles. Non-catalyst material is melted andpooled in interstitial regions. In some embodiments, the non-catalystmaterial may be mixed with the diamond particles prior to initiation ofthe HPHT process. In other embodiments, the non-catalyst material may beswept into the interstitial regions between the diamond particles duringthe HPHT process from an external source. In yet other embodiments, thenon-catalyst material may be both mixed with the diamond particles priorto initiation of the HPHT process and swept into the interstitialregions between the diamond particles during the HPHT process from anexternal source.

Subsequent to melting of the non-catalyst material, the catalystmaterial may be melted. The non-catalyst material and the catalystmaterial may be selected such that the melting or liquidus temperatureof the non-catalyst material is lower than the melting or liquidustemperature of the catalyst material. In some embodiments, the meltingor liquidus temperature of the non-catalyst material may be lower thanthe solidus temperature of the catalyst material. In some embodiments,the catalyst material may be mixed with the diamond particles prior toinitiation of the HPHT process. In other embodiments, the catalystmaterial may be swept into the interstitial regions between the diamondparticles during the HPHT process from an external source, for example asubstrate having a metal carbide composition that includes catalystmaterial. In yet other embodiments, the catalyst material may be bothmixed with the diamond particles prior to initiation of the HPHT processand swept into the interstitial regions between the diamond particlesduring the HPHT process from an external source.

With the catalyst material molten in a liquid state, the catalyst maydissolve at least a portion of the carbon from the diamond particles. Asis conventionally known, the molten catalyst material may act as asolvent catalyst that diamond may re-precipitate from, such that thediamond particles form diamond-to-diamond bonds between one another,thereby forming a polycrystalline diamond body. The polycrystallinediamond body includes a plurality of diamond grains that are coupled toone another through diamond-to-diamond bonds, and having a plurality ofinterstitial regions positioned therebetween. A significant portion ofthe interstitial regions between the diamond grains are connected to oneanother such that the interstitial regions form an interconnectednetwork of interstitial regions. The interconnected network ofinterstitial regions can be penetrated by a leaching agent during theprocess of catalyst removal from the polycrystalline diamond body, aswill be discussed in greater detail below. However, some of theinterstitial regions within the polycrystalline diamond body may be“trapped” such that they are separated from the interconnected networkof interstitial regions and therefore cannot be penetrated by theleaching region. The interstitial regions between the diamond grains maybe filled with non-catalyst material, catalyst material, metal carbide,or combinations thereof. The polycrystalline diamond body may beattached to a substrate.

As conventionally known, the diamond body may be contacted with aleaching agent that removes at least a portion of the materials presentin the interstitial regions that are positioned proximate to thelocation of leaching agent application. For example, the polycrystallinediamond body may be submerged in a leaching agent such that surfaces ofthe polycrystalline diamond body contact the leaching agent, whilesurfaces of the substrate, to which the polycrystalline diamond body areattached, are maintained spaced apart from contact with the leachingagent. The leaching agent may be selected to attack the non-catalystmaterial and the catalyst material while preserving the diamond grains.

The non-catalyst material and the catalyst material may undergo chemicalreaction with the leaching agent. The non-catalyst material may be morereactive with the leaching agent than the catalyst material such thatthe rate of reaction is higher for the non-catalyst material than forthe catalyst material, and such that the rate of material removal byleaching is higher for diamond bodies formed with non-catalyst materialand catalyst material as compared to diamond bodies formed without theintroduction of non-catalyst material.

In one embodiment, the combined leaching of the catalyst material andthe non-catalyst material may exceed a conventional leaching rate by atleast about 30%. A conventional leaching rate is discussed in furtherdetail below. In another embodiment, the combined leaching rate of thecatalyst material and the non-catalyst material may exceed theconvention leaching rate by at least about 40%. In yet anotherembodiment, the combined leaching rate of the catalyst material and thenon-catalyst material may exceed the convention leaching rate profile byup to about 60%. In one embodiment, a leached depth of 800 μm from theworking surface of the polycrystalline diamond body is achieved in lessthan about 7 days of exposure to the leaching agent. In comparison, aleached depth of 800 μm from the working surface of a polycrystallinediamond body according to the conventional leaching rate is achieved inabout 10 days of exposure to the leaching agent.

The incorporation of non-catalyst material into the diamond body duringthe HPHT process may result in a decrease in the total catalyst contentboth prior to and following leaching as compared to conventional cuttingelements that do not include non-catalytic material. The decrease incatalyst content as compared to conventional cutting elements mayincrease cutting element life by decreasing internal mechanical stressesattributable to mismatch between the coefficients of thermal expansionand modulus of the diamond grains, the non-catalytic material, and thecatalytic material, and any back-conversion to non-diamond forms ofcarbon, which may be accelerated due to the presence of catalystmaterial. Further, the increase in leaching rate may reducemanufacturing time associated with producing a cutting element accordingto embodiments disclosed herein, in particular, by reducing the cycletime associated with leaching the non-catalytic material and catalyticmaterial from the interstitial regions of the diamond body.

Additionally, the incorporation of non-catalyst material into thediamond body during the HPHT process may result in a decrease in themetal carbide concentration in the diamond body as compared toconventional diamond bodies made without the introduction ofnon-catalyst materials. Metal carbides are typically introduced to thediamond bodies during the HPHT process from the substrate, which, in oneexample, may be made from a cemented tungsten carbide. In oneembodiment, the metal carbide concentration within diamond bodiesaccording to the present disclosure may be less than 70% of the metalcarbide concentration of a conventional diamond body, for example beingless than about 50% of the metal carbide concentration of a conventionaldiamond body, for example being less than about 30% of the metal carbideconcentration of a conventional diamond body.

In one manufacturing process, cutting elements may be produced in a“single press” HPHT process in which diamond particles are bonded to oneanother and a substrate to form a cutting element having an integraldiamond body with diamond grains bonded to one another indiamond-to-diamond bonds and interstitial regions between the diamondgrains. Some of the interstitial regions include non-catalyst material,catalyst material, metal carbide, or combinations thereof. Portions ofthe diamond body are maintained in contact with a leaching agent thatremoves substantially all of the non-catalyst material and catalystmaterial from a leached region positioned at the working surface of thecutting element and extending toward the substrate to a transition zonein which the leached region abuts the unleached region that is rich withnon-catalyst material and catalyst material.

Referring now to FIG. 3, a flowchart depicting a manufacturing procedure400 is provided. Diamond particles 90 are mixed with the non-catalystmaterial 92 in step 402. The size of the diamond particles 90 may beselected based on the desired mechanical properties of thepolycrystalline diamond cutting element that is finally produced. It isgenerally believed that a decrease in grain size increases the abrasionresistance of the polycrystalline diamond cutting element, but decreasesthe toughness of the polycrystalline diamond cutting element. Further,it is generally believed that a decrease in grain size results in anincrease in interstitial volume of the PCD compact. In one embodiment,the diamond particles 90 may have a single mode median volumetricparticle size distribution (D50) in a range from about 10 μm to about100 μm, for example having a D50 in a range from about 14 μm to about 50μm, for example having a D50 of about 30 μm to about 32 μm. In otherembodiments, the diamond particles 90 may have a D50 of about 14 μm, orabout 17 μm, or about 30 μm, or about 32 μm. In other embodiments, thediamond particles 90 may have a multimodal particle size, wherein thediamond particles 90 are selected from two or more single modepopulations having different values of D50, including multimodaldistributions having two, three, or four different values of D50.

The non-catalyst material 92 may be introduced to step 402 as a powder.In other embodiments, the non-catalyst material 92 may be coated ontothe unbonded diamond particles. The particle size of the non-catalystmaterial may be in a range from about 0.005 μm to about 100 μm, forexample being in a range from about 10 μm to about 50 μm. Thenon-catalyst material 92 may be coated onto the unbounded diamondparticles by conventionally-known coating techniques, including, forexample, chemical vapor deposition, physical vapor deposition, thin filmdeposition, electrochemical plating, electroless plating, thermalspraying, and the like.

The diamond particles 90 and the non-catalyst material 92 may be drymixed with one another using, for example, a commercial TURBULA®Shaker-Mixer available from Glen Mills, Inc. of Clifton, N.J. or anacoustic mixer available from Resodyn Acoustic Mixers, Inc. of Butte,Mont. to provide a generally uniform and well mixed combination. Inother embodiments, the mixing particles may be placed inside a bag orcontainer and held under vacuum or in a protective gas atmosphere duringthe blending process.

In other embodiments, the non-catalyst material 92 may be positionedseparately from the diamond particles 90. During the first HPHT process,the non-catalyst materials 92 may “sweep” from their original locationand through the diamond particles 90, thereby positioning thenon-catalyst materials 92 prior to sintering of the diamond particles90. Subsequent to sweeping of the non-catalyst materials 92, thecatalyst material 94 may be swept through the diamond particles 90during the first HPHT process, thereby promoting formation ofinter-diamond bonds between the diamond particles 90 and sintering ofthe diamond particles 90 to form the polycrystalline diamond body 120 ofthe polycrystalline diamond compact 80.

The diamond particles 90 and the non-catalyst material 92 may bepositioned within a cup 142 that is made of a refractory material, forexample tantalum, niobium, vanadium, molybdenum, tungsten, or zirconium,as shown in step 404. The support substrate 144 is positioned along anopen end of the cup 142 and is optionally welded to the cup 142 to formcell assembly 140 that encloses diamond particles 90 and thenon-catalyst material 92. The support substrate 144 may be selected froma variety of hard phase materials including, for example, cementedtungsten carbide, cemented tantalum carbide, or cemented titaniumcarbide. In one embodiment, the support substrate 144 may includecemented tungsten carbide having free carbons, as described in U.S.Provisional Application Nos. 62/055,673, 62/055,677, and 62/055,679, theentire disclosures of which are hereby incorporated by reference. Thesupport substrate 144 may include a pre-determined quantity of catalystmaterial 94. Using a cemented tungsten carbide-cobalt system as anexample, the cobalt is the catalyst material 94 that is infiltrated intothe diamond particles 90 during the HPHT process. In other embodiments,the cell assembly 140 may include additional catalyst material (notshown) that is positioned between the support substrate 144 and thediamond particles 90. In further other embodiments, the cell assembly140 may include non-catalyst material 92 that is positioned between thediamond particles 90 and the support substrate 144 or between thediamond particles 90 and the additional catalyst material (not shown).

The cell assembly 140, which includes the diamond particles 90, thenon-catalyst material 92, and the support substrate 144, is introducedto a press that is capable of and adapted to introduce ultra-highpressures and elevated temperatures to the cell assembly 140 in an HPHTprocess, as shown in step 408. The press type may be a belt press, acubic press, or other suitable presses. The pressures and temperaturesof the HPHT process that are introduced to the cell assembly 140 aretransferred to contents of the cell assembly 140. In particular, theHPHT process introduces pressure and temperature conditions to thediamond particles 90 at which diamond is stable and inter-diamond bondsform. The temperature of the HPHT process may be at least about 1000° C.(e.g., about 1200° C. to about 1800° C., or about 1300° C. to about1600° C.) and the pressure of the HPHT process may be at least 4.0 GPa(e.g., about 4.0 GPa to about 12.0 GPa, or about 5.0 GPa to about 10GPa, or about 5.0 GPa to about 8.0 GPa) for a time sufficient foradjacent diamond particles 90 to bond to one another, thereby forming anintegral PCD compact having the polycrystalline diamond body 120 and thesupport substrate 144 that are bonded to one another.

The introduction of the non-catalyst material 92 to the polycrystallinediamond body 120 prior to the HPHT process may result in a reduction ofcatalyst material 94 that is present in the polycrystalline diamond body120 following the HPHT process and prior to initiation of any subsequentleaching process. As compared to conventional cutting elements that areproduced without the introduction of the non-catalyst material 92,unleached diamond bodies 120 produced according to the presentdisclosure may contain, for example, about 10% less catalyst material 94when evaluated prior to leaching.

The polycrystalline diamond body 120 may undergo a leaching process inwhich the catalyst material is removed from the polycrystalline diamondbody 120. In one example of a leaching process, the polycrystallinediamond body 120 is introduced to a leaching agent of an acid bath toremove the remaining support substrate 144 from the polycrystallinediamond body 120, as shown in step 412. The leaching process may alsoremove non-catalyst material 92 and catalyst material 94 from thepolycrystalline diamond body 120 that is accessible to the acid.Suitable acids may be selected based on the solubility of thenon-catalyst material 92 and the catalyst material 94 that is present inthe polycrystalline diamond body. Examples of such acids include, forexample and without limitation, ferric chloride, cupric chloride, nitricacid, hydrochloric acid, hydrofluoric acid, aqua regia, or solutions ormixtures thereof. The acid bath may be maintained at an pre-selectedtemperature to modify the rate of removal of the non-catalyst material92 and the catalyst material 94 from the polycrystalline diamond body120, including being in a temperature range from about 10° C. to aboutthe boiling point of the leaching agent. In some embodiments, the acidbath may be maintained at elevated pressures that increase the liquidboiling temperature and thus allow the use of elevated temperatures, forexample being at a temperature of greater than the boiling point of theleaching agent. The polycrystalline diamond body 120 may be subjected tothe leaching process for a time sufficient to remove the desiredquantity of non-catalyst material 92 and catalyst material 94 from thepolycrystalline diamond body. The polycrystalline diamond body 120 maybe subjected to the leaching process for a time that ranges from aboutone hour to about one month, including ranging from about one day toabout 7 days.

In some embodiments, the polycrystalline diamond body 120 may bemaintained in the leaching process until the polycrystalline diamondbody 120 is at least partially leached. In polycrystalline diamondbodies 120 that are partially leached, the exterior regions of thepolycrystalline diamond bodies 120 that are positioned along the outersurfaces of the polycrystalline diamond bodies 120 have the accessibleinterstitial regions depleted of non-catalyst material 92 and/orcatalyst material 94, while the interior regions of the polycrystallinediamond bodies 120 are rich with non-catalyst material 92 and/orcatalyst material 94. In such partially leached polycrystalline diamondbodies 120, all of the accessible interstitial regions between thediamond grains may be fully depleted of non-catalyst material 92 and/orcatalyst material 94. In some embodiments, metal carbide that isintroduced to the polycrystalline diamond body 120 during the HPHTprocess may remain in the accessible interstitial regions.

In some embodiments, the extent of the leaching may be monitored byweighing the polycrystalline diamond body 120 after a pre-defined periodof time. As the change in the weight loss of the polycrystalline diamondbody 120 approaches a threshold value (for example, about 10.5% loss ofthe unleached polycrystalline diamond body 120), the polycrystallinediamond body 120 may be considered to be completely leached. The weightloss threshold value may vary with the type of PCD body depend on, forexample, the diamond grain size, type and amount of added non-catalystmaterial, and the like. Because the polycrystalline diamond body 120 isleached without the support substrate 144, the leach fronts may extendfrom opposing sides of the polycrystalline diamond body 120 and from theperimeter surface of the polycrystalline diamond body 120. When theleach fronts from the opposing sides of the polycrystalline diamond body120 meet, the polycrystalline diamond body 120 may be considered to becompletely leached. In some embodiments, the extent of leaching may bemonitored by the loss of density of the diamond body.

In some embodiments, an unleached polycrystalline diamond body may havenon-catalyst material 92 and catalyst material 94 at greater than about4 vol. % of the polycrystalline diamond body 120, including being fromabout 4 vol. % to about 15 vol. %. In comparison, a completely leachedportion of a polycrystalline diamond body 120 may have non-catalystmaterial 92 and catalyst material 94 that is less than about 50% lessthan the unleached polycrystalline diamond body 120, for example atabout 42 vol. % less than the polycrystalline diamond body 120. Acompletely leached polycrystalline diamond body 120 may havenon-catalyst material 92 and catalyst material 94 being from about 0.25vol. % to about 6 vol. %, for example, being from about 0.2 vol. % toabout 1 vol. %. In general, the extent of loss of non-catalyst materialand catalyst material in a completely leached polycrystalline diamondbody 120 is determined the material structure and composition, forexample by the precursor diamond grain size and the particle sizedistribution.

As discussed above, the introduction of the non-catalyst material to thepolycrystalline diamond body 120 reduces the concentration of thecatalyst material 94 in the polycrystalline diamond body 120 prior toleaching. The introduction of the non-catalyst material 92 to thepolycrystalline diamond body 120 also reduces the concentration of thetrapped catalyst material 94 that remains present in the trappedinterstitial volumes of the polycrystalline diamond body 120 followingcomplete leaching of the polycrystalline diamond body 120. As comparedto conventional cutting elements that are produced without theintroduction of the non-catalyst material 92, diamond bodies 120produced according to the present disclosure contain from about 30 vol.% to about 90 vol. % less catalyst material 94 following completeleaching of both of the compared diamond bodies.

The introduction of the non-catalyst material 92 to the polycrystallinediamond body 120 may also increase the leaching rate of thepolycrystalline diamond body 120, such that the duration of timerequired to obtain complete leaching of the polycrystalline diamond body120 is reduced as compared to conventionally produced diamond bodies.For example, complete leaching of the polycrystalline diamond body 120having non-catalyst material 92 according to the present disclosure maybe obtained from about 30% to about 60% less time as compared toconventional cutting elements that are produced without the introductionof the non-catalyst material 92. In one example, when evaluated after 7days of introduction to the leaching process, polycrystalline diamondbodies 120 produced according to the present disclosure exhibited fromabout 40% to about 70% more mass loss than conventional PCD compacts.

Following complete leaching of the polycrystalline diamond body 120, thepolycrystalline diamond body 120 continues to exhibit non-diamondcomponents that are present in the trapped interstitial regions of thepolycrystalline diamond body 120 that are positioned between bondeddiamond grains in at least detectable amounts. However, the reduction ofthe non-diamond components (including catalyst material 94) in theleaching process accessible interstitial regions reduces the content ofcatalyst material 94 in the polycrystalline diamond body 120 andincreases the thermal stability of the polycrystalline diamond body 120.

Following formation of the integral PCD compact 82, the PCD compact 82may be processed through a variety of finishing operations to removeexcess material from the PCD compact 82 and configure the PCD compact 82for use by an end user, including formation of a cutting element 84, asshown in step 418. Such finishing operations may include, for example,grinding and polishing the outside diameter of the PCD compact 82,cutting, grinding, lapping, and polishing the opposing faces (both thesupport-substrate-side face and the diamond-body-side face) of the PCDcompact 82, and grinding and lapping a chamfer into the PCD compact 82between the diamond-body-side face and the outer diameter of the PCDcompact 82.

In an alternative manufacturing process, cutting elements may beproduced in a “double press” HPHT process in which diamond particles arebonded to one another to form the diamond body in a first HPHT process,the diamond body is fully leached of non-catalyst material and catalystmaterial from the accessible interstitial volumes between the diamondgrains, and the diamond body is attached to a substrate in a second HPHTprocess. The diamond particles may first be subjected to a first HPHTprocess to form a polycrystalline diamond compact having apolycrystalline diamond body that is formed through sintering with acatalyst material source. In one embodiment, the catalyst materialsource is provided integrally with a support substrate (a first supportsubstrate). Substantially all of the support substrate is removed fromthe polycrystalline diamond body, the polycrystalline diamond body ismachined to a desired shape, and the polycrystalline diamond body isleached to remove substantially all of the accessible non-catalystmaterial and catalyst material from the interstitial spaces of thepolycrystalline diamond body. The leached polycrystalline diamond bodyis subsequently cleaned of leaching debris and bonded to a supportsubstrate in a second HPHT process, thus forming a PCD compact. This PCDcompact is subsequently finished according to conventionally knownprocedures to the final shape desirable for the end user application.

Referring now to FIG. 4, a flowchart depicting a manufacturing procedure200 is provided. Diamond particles 90 are mixed with the non-catalystmaterial 92 in step 202. The size of the diamond particles 90 may beselected based on the desired mechanical properties of thepolycrystalline diamond cutting element that is finally produced. It isgenerally believed that a decrease in grain size increases the abrasionresistance of the polycrystalline diamond cutting element, but decreasesthe toughness of the polycrystalline diamond cutting element. Further,it is generally believed that a decrease in grain size results in anincrease in interstitial volume of the PCD compact. The porosityrepresents the total accessible interstitial space of thepolycrystalline diamond body. In one embodiment, the diamond particles90 may have a single mode median volumetric particle size distribution(D50) in a range from about 10 μm to about 100 μm, for example having aD50 in a range from about 14 μm to about 50 μm, for example having a D50of about 30 μm to about 32 μm. In other embodiments, the diamondparticles 90 may have a D50 of about 14 μm, or about 17 μm, or about 30μm, or about 32 μm. In other embodiments, the diamond particles 90 mayhave a multimodal particle size, wherein the diamond particles 90 areselected from two or more single mode populations having differentvalues of D50, including multimodal distributions having two, three, orfour different values of D50.

The non-catalyst material 92 may be introduced to step 202 as a powder.In other embodiments, the non-catalyst material 92 may be coated ontothe unbonded diamond particles. The particle size of the non-catalystmaterial may be in a range from about 0.005 μm to about 100 μm, forexample being in a range from about 10 μm to about 50 μm. In someembodiments, the coating of the non-catalyst material 92 onto theunbounded diamond particles may be in a range from about 0.001 μm toabout 10 μm.

The diamond particles 90 and the non-catalyst material 92 may be drymixed with one another using, for example, a commercial TURBULA®Shaker-Mixer available from Glen Mills, Inc. of Clifton, N.J. or anacoustic mixer available from Resodyn Acoustic Mixers, Inc. of Butte,Mont. to provide a generally uniform and well mixed combination. Inother embodiments, the mixing particles may be placed inside a bag orcontainer and held under vacuum or in a protective atmosphere during theblending process.

In other embodiments, the non-catalyst material 92 may be positionedseparately from the diamond particles 90. During the first HPHT process,the non-catalyst materials 92 may “sweep” from their original locationand through the diamond particles 90, thereby positioning thenon-catalyst materials 92 prior to sintering of the diamond particles90. Subsequent to sweeping of the non-catalyst materials 92, thecatalyst material 94 may be swept through the diamond particles 90during the first HPHT process, thereby promoting formation ofinter-diamond bonds between the diamond particles 90 and sintering ofthe diamond particles 90 to form the polycrystalline diamond body 120 ofthe polycrystalline diamond compact 80.

The diamond particles 90 and the non-catalyst material 92 may bepositioned within a cup 142 that is made of a refractory material, forexample tantalum, niobium, vanadium, molybdenum, tungsten, or zirconium,as shown in step 204. The support substrate 144 is positioned along anopen end of the cup 142 and is optionally welded to the cup 142 to formcell assembly 140 that encloses diamond particles 90 and thenon-catalyst material 92. The support substrate 144 may be selected froma variety of hard phase materials including, for example, cementedtungsten carbide, cemented tantalum carbide, or cemented titaniumcarbide. In one embodiment, the support substrate 144 may includecemented tungsten carbide having free carbons, as described in U.S.Provisional Application Nos. 62/055,673, 62/055,677, and 62/055,679, theentire disclosures of which are hereby incorporated by reference. Thesupport substrate 144 may include a pre-determined quantity of catalystmaterial 94. Using a cemented tungsten carbide-cobalt system as anexample, the cobalt is the catalyst material 94 that is infiltrated intothe diamond particles 90 during the HPHT process. In other embodiments,the cell assembly 140 may include additional catalyst material (notshown) that is positioned between the support substrate 144 and thediamond particles 90. In further other embodiments, the cell assembly140 may include non-catalyst material 92 that is positioned between thediamond particles 90 and the support substrate 144 or between thediamond particles 90 and the additional catalyst material (not shown).

The cell assembly 140, which includes the diamond particles 90, thenon-catalyst material 92, and the support substrate 144, is introducedto a press that is capable of and adapted to introduce ultra-highpressures and elevated temperatures to the cell assembly 140 in an HPHTprocess, as shown in step 208. The press type may be a belt press, acubic press, or other suitable presses. The pressures and temperaturesof the HPHT process that are introduced to the cell assembly 140 aretransferred to contents of the cell assembly 140. In particular, theHPHT process introduces pressure and temperature conditions to thediamond particles 90 at which diamond is stable and inter-diamond bondsform. The temperature of the HPHT process may be at least about 1000° C.(e.g., about 1200° C. to about 1800° C., or about 1300° C. to about1600° C.) and the pressure of the HPHT process may be at least 4.0 GPa(e.g., about 4.0 GPa to about 12.0 GPa, or about 5.0 GPa to about 10GPa, or about 5.0 GPa to about 8.0 GPa) for a time sufficient foradjacent diamond particles 90 to bond to one another, thereby forming anintegral PCD compact having the polycrystalline diamond body 120 and thesupport substrate 144 that are bonded to one another.

Subsequent to formation of the integral PCD, the polycrystalline diamondbody 120 may be separated from the support substrate 144 using a varietyof conventionally known techniques, including chemically dissolution andmachining techniques, such as grinding, electrical discharge machining,or laser ablation, as shown in step 210. The polycrystalline diamondbody 120 may be separated from a majority of the support substrate 144with a portion of the support substrate 144 remaining integral with thepolycrystalline diamond body 120. Following removal of the supportsubstrate 144, the polycrystalline diamond body 120 is machined to adesired shape for subsequent processing. The polycrystalline diamondbody 120 may be shaped into a cylindrical shaped disc in which generallyplanar faces and a generally cylindrical body of the polycrystallinediamond body 120 are formed.

The introduction of the non-catalyst material 92 to the polycrystallinediamond body 120 prior to the first HPHT process may result in areduction of catalyst material 94 that is present in the polycrystallinediamond body 120 following the HPHT process and prior to initiation ofany subsequent leaching process. As compared to conventional cuttingelements that are produced without the introduction of the non-catalystmaterial 92, unleached diamond bodies 120 produced according to thepresent disclosure may contain, for example, about 10% less catalystmaterial 94 when evaluated prior to leaching.

The polycrystalline diamond body 120 may undergo a leaching process inwhich the catalyst material is removed from the polycrystalline diamondbody 120. In one example of a leaching process, the polycrystallinediamond body 120 is introduced to a leaching agent of an acid bath toremove the remaining support substrate 144 from the polycrystallinediamond body 120, as shown in step 212. The leaching process may alsoremove non-catalyst material 92 and catalyst material 94 from thepolycrystalline diamond body 120 that is accessible to the acid.Suitable acids may be selected based on the solubility of thenon-catalyst material 92 and the catalyst material 94 that is present inthe polycrystalline diamond body. Examples of such acids include, forexample and without limitation, ferric chloride, cupric chloride, nitricacid, hydrochloric acid, hydrofluoric acid, aqua regia, or solutions ormixtures thereof. The acid bath may be maintained at an pre-selectedtemperature to modify the rate of removal of the non-catalyst material92 and the catalyst material 94 from the polycrystalline diamond body120, including being in a temperature range from about 10° C. to aboutthe boiling point of the leaching agent. In some embodiments, the acidbath may be maintained at elevated pressures that increase the liquidboiling temperature and thus allow the use of elevated temperatures, forexample being at a temperature of greater than the boiling point of theleaching agent. The polycrystalline diamond body 120 may be subjected tothe leaching process for a time sufficient to remove the desiredquantity of non-catalyst material 92 and catalyst material 94 from thepolycrystalline diamond body. The polycrystalline diamond body 120 maybe subjected to the leaching process for a time that ranges from aboutone hour to about one month, including ranging from about one day toabout 7 days.

In some embodiments, the polycrystalline diamond body 120 may bemaintained in the leaching process until the polycrystalline diamondbody 120 is at least partially leached. In polycrystalline diamondbodies 120 that are partially leached, the exterior regions of thepolycrystalline diamond bodies 120 that are positioned along the outersurfaces of the polycrystalline diamond bodies 120 have the accessibleinterstitial regions depleted of non-catalyst material 92 and/orcatalyst material 94, while the interior regions of the polycrystallinediamond bodies 120 are rich with non-catalyst material 92 and/orcatalyst material 94. In other embodiments, the polycrystalline diamondbody 120 may be maintained in the acid bath until complete leaching ofthe polycrystalline diamond body 120 is realized. Complete leaching ofthe polycrystalline diamond body 120 may be defined as removal from thepolycrystalline diamond body 120 of all of the non-catalyst material 92and the catalyst material 94 that is accessible to the leaching media.

In some embodiments, the extent of the leaching may be monitored byweighing the polycrystalline diamond body 120 after a pre-defined periodof time. As the change in the weight loss of the polycrystalline diamondbody 120 approaches a threshold value (for example, 10% loss of theunleached polycrystalline diamond body 120), the polycrystalline diamondbody 120 may be considered to be completely leached. Because thepolycrystalline diamond body 120 is leached without the supportsubstrate 144, the leach fronts may extend from opposing sides of thepolycrystalline diamond body 120 and from the perimeter surface of thepolycrystalline diamond body 120. When the leach fronts from theopposing sides of the polycrystalline diamond body 120 meet, thepolycrystalline diamond body 120 may be considered to be completelyleached. In some embodiments, the extent of leaching may be monitored bythe loss of density of the diamond body.

While some diamond bodies 120 may be at least partially leached,reference is made below to a completely leached polycrystalline diamondbody 120 to discuss the effects of the addition of the non-catalystmaterial 92 to the polycrystalline diamond body 120.

In some embodiments, an unleached polycrystalline diamond body may havenon-catalyst material 92 and catalyst material 94 at greater than about4 vol. % of the polycrystalline diamond body 120, including being fromabout 4 vol. % to about 15 vol. %. In comparison, a completely leachedpolycrystalline diamond body 120 may have non-catalyst material 92 andcatalyst material 94 that is less than about 50% less than the unleachedpolycrystalline diamond body 120, for example at about 42 vol. % lessthan the polycrystalline diamond body 120. A completely leachedpolycrystalline diamond body 120 may have non-catalyst material 92 andcatalyst material 94 being from about 0.25 vol. % to about 6 vol. %, forexample, being from about 0.2 vol. % to about 1 vol. %. In general, theextent of loss of non-catalyst material and catalyst material in acompletely leached polycrystalline diamond body 120 is determined thematerial structure and composition, for example by the precursor diamondgrain size and the particle size distribution.

As discussed above, the introduction of the non-catalyst material to thepolycrystalline diamond body 120 reduces the concentration of thecatalyst material 94 in the polycrystalline diamond body 120 prior toleaching. The introduction of the non-catalyst material 92 to thepolycrystalline diamond body 120 also reduces the concentration of thetrapped catalyst material 94 that remains present in the trappedinterstitial volumes of the polycrystalline diamond body 120 followingcomplete leaching of the polycrystalline diamond body 120. As comparedto conventional cutting elements that are produced without theintroduction of the non-catalyst material 92, diamond bodies 120produced according to the present disclosure contain from about 30 vol.% to about 90 vol. % less catalyst material 94 following completeleaching of both of the compared diamond bodies.

The introduction of the non-catalyst material 92 to the polycrystallinediamond body 120 may also increase the leaching rate of thepolycrystalline diamond body 120, such that the duration of timerequired to obtain complete leaching of the polycrystalline diamond body120 is reduced as compared to conventionally produced diamond bodies.For example, complete leaching of the polycrystalline diamond body 120having non-catalyst material 92 according to the present disclosure maybe obtained from about 30% to about 60% less time as compared toconventional cutting elements that are produced without the introductionof the non-catalyst material 92. In one example, when evaluated after 7days of introduction to the leaching process, polycrystalline diamondbodies 120 produced according to the present disclosure exhibited fromabout 40% to about 70% more mass loss than conventional PCD compacts.

Following complete leaching of the polycrystalline diamond body 120, thepolycrystalline diamond body 120 continues to exhibit non-diamondcomponents that are present in the trapped interstitial regions of thepolycrystalline diamond body 120 that are positioned between bondeddiamond grains in at least detectable amounts. However, the reduction ofthe non-diamond components (including catalyst material 94) in theleaching process accessible interstitial regions reduces the content ofcatalyst material 94 in the polycrystalline diamond body 120 andincreases the thermal stability of the polycrystalline diamond body 120.

Referring again to FIG. 4, the completely leached polycrystallinediamond body 120 is assembled into a second cell in which thepolycrystalline diamond body 120 is attached to a support substrate 110(a second support substrate 110) and optionally a crown precursormaterial 400, as shown in step 214. The polycrystalline diamond body 120is positioned proximate to the support substrate 110 and assembled intoa cell assembly 240. The support substrate 110 may be selected from avariety of hard phase materials including, for example, cementedtungsten carbide, cemented tantalum carbide, or cemented titaniumcarbide. In one embodiment, the support substrate 110 may includecemented tungsten carbide having free carbons, as described in U.S.Provisional Application Nos. 62/055,673, 62/055,677, and 62/055,679, theentire disclosures of which are hereby incorporated by reference. Thissecond support substrate 110 may be made from the same material as thefirst support substrate 144 discussed above. Alternatively, the secondsupport substrate 110 may be made from a dissimilar material from thefirst support substrate 144 discussed above. The support substrate 110may include a quantity of catalyst material 94. The support substrate144 may have an intergranular phase liquidus temperature below 1300° C.at high pressure conditions. Using a cemented tungsten carbide-cobaltsystem as an example, the cobalt is the catalyst material 94 that isinfiltrated into the at least partially leached polycrystalline diamondbody 120 during a second HPHT process. In other embodiments, the cellassembly 240 may include additional catalyst material (not shown) thatis positioned between the support substrate 110 and the polycrystallinediamond body 120. The cell assembly 240 includes pressure transferringagent 152 that at least partially surround the polycrystalline diamondbody 120 and the support substrate 110.

The cell assembly 140, which includes the polycrystalline diamond body120 and the support substrate 110, is introduced to a press that iscapable of and adapted to introduce ultra-high pressures and elevatedtemperatures to the cell assembly 140 in a second HPHT process, as shownin step 216. The pressures and temperatures of the HPHT process that areintroduced to the cell assembly 140 are transferred to contents of thecell assembly 140. In particular, the HPHT process introduces pressureand temperature conditions to the polycrystalline diamond body 120 atwhich diamond phase is thermodynamically stable. In other embodiments,the HPHT process introduces pressure and temperature conditions to thepolycrystalline diamond body 120 at which diamond phase is unstable,which may lead to the formation of non-diamond carbon forms. Thetemperature of the HPHT process may be selected to be above the meltingtemperature of the infiltrating material. In one embodiment, the HPHTprocess may be operated at a temperature of at least about 1000° C.(e.g., about 1200° C. to about 1600° C., or about 1200° C. to about1300° C.) and the pressure of the HPHT process may be at least 4.0 GPa(e.g., about 5.0 GPa to about 12.0 GPa, or about 5.0 GPa to about 10.0GPa, or about 6.0 GPa to about 7.5 GPa) for a time sufficient forcatalyst material 94 to infiltrate the polycrystalline diamond body 120,thereby bonding the polycrystalline diamond body 120 to the supportsubstrate 110 and forming an integral PCD compact 82.

Following formation of the integral PCD compact 82, the PCD compact 82may be processed through a variety of finishing operations to removeexcess material from the PCD compact 82 and configure the PCD compact 82for use by an end user, including formation of a PCD cutting element 84,as shown in step 218. Such finishing operations may include, forexample, grinding and polishing the outside diameter of the PCD compact82, cutting, grinding, lapping, and polishing the opposing faces (boththe support-substrate-side face and the diamond-body-side face) of thePCD compact 82, and grinding and lapping a chamfer into the PCD compact82 between the diamond-body-side face and the outer diameter of the PCDcompact 82.

Referring now to FIG. 5, a plurality of PCD cutting elements 100according to the present disclosure may be installed in a drill bit 310,as conventionally known, to perform a downhole drilling operation. Thedrill bit 310 may be positioned on a drilling assembly 300 that includesa drilling motor 302 that applies torque to the drill bit 310 and anaxial drive mechanism 304 that is coupled to the drilling assembly formoving the drilling assembly 300 through a borehole 60 and operable tomodify the axial force applied by the drill bit 310 in the borehole 60.Force applied to the drill bit 310 is referred to as Weight on Bit”(“WOB”). The drilling assembly 300 may also include a steering mechanismthat modifies the axial orientation of the drill assembly 300, such thatthe drill bit 310 can be positioned for non-linear downhole drilling.

The drill bit 310 includes a stationary portion 312 and a materialremoval portion 314. The material removal portion 314 may rotaterelative to the stationary portion 312. Torque applied by the drillingmotor 302 rotates the material removal portion 314 relative to thestationary portion 312. A plurality of PCD cutting elements 100according to the present disclosure are coupled to the material removalportion 314. The plurality of PCD cutting elements 100 may be coupled tothe material removal portion 314 by a variety of conventionally knownmethods, including attaching the plurality of PCD cutting elements 100to a corresponding plurality of shanks 316 that are coupled to thematerial removal portion 314. The PCD cutting elements 100 may becoupled to the plurality of shanks 316 by a variety of methods,including, for example, brazing, adhesive bonding, or mechanicalaffixation. In embodiments in which the PCD cutting elements 100 arebrazed to the shanks 316 with a braze filler 318, at least a portion ofthe shanks 316, the braze filler 318, and at least a portion of thesupport substrate 110 of the PCD cutting element 100 is heated to anelevated temperature while in contact with one another. As thecomponents decrease in temperature, the braze filler 318 solidifies andforms a bond between the support substrate 110 of the PCD cuttingelement 100 and the shanks 316 of the material removal portion 314. Inone embodiment, the brazing filler 318 has a melting temperature that isgreater than a melting temperature of the non-catalyst material 92 ofthe polycrystalline diamond body 120 at ambient pressure conditions. Inanother embodiment, the brazing filler 318 has a melting temperaturethat is less than the catalyst material 94 of the polycrystallinediamond body 120 at ambient pressure conditions. In yet anotherembodiment, the brazing filler 318 has a melting temperature that isless than the liquidus temperature of the catalyst material 94 of thepolycrystalline diamond body at ambient pressure conditions.

When the drill bit 310 is positioned in the borehole 60, the materialremoval portion 314 rotates about the stationary portion 312 toreposition the PCD cutting elements 100 relative to the borehole 60,thereby removing surrounding material from the borehole 60. Force isapplied to the drill bit 310 by the axial drive mechanism 304 ingenerally the axial orientation of the drill bit 310. The axial drivemechanism 304 may increase the WOB, thereby increasing the contact forcebetween the PCD cutting elements 100 and the material of the borehole60. As the material removal portion 314 of the drill bit 310 continuesto rotate and WOB is maintained on the drill bit 310, the PCD cuttingelements 100 abrade material of the borehole 60, and continue the pathof the borehole 60 in an orientation that generally corresponds to theaxial direction of the drill bit 310.

The temperature of the PCD cutting elements 100 may increase withincreasing WOB, increasing material removal rates, and increasingcutting element wear. As discussed hereinabove, the increase intemperature may contribute to an increase in cutting element wear causeby back-conversion of diamond to non-diamond carbon forms. Further, theincrease in temperature may increase stresses in the diamond latticecaused by mismatch in the coefficients of thermal expansion of thediamond grains and the catalyst material. In some embodiments, theoperating temperature of the PCD cutting elements 100 at locationsproximate to contact with the borehole 60 may have a temperature ofgreater than about 400° C., including having a temperature of greaterthan about 500° C., including having a temperature of greater than about600° C., including have a temperature of greater than about 700° C. Insome embodiments, the operating temperature of the PCD cutting elements100 at locations proximate to contact with the borehole 60 may begreater than the melting temperature of the non-catalyst material 92 ofthe polycrystalline diamond body 120.

It should now be understood that PCD cutting elements according to thepresent disclosure include a polycrystalline diamond body that iscoupled to a substrate. The polycrystalline diamond body has a pluralityof diamond grains that define a plurality of interstitial regionsbetween bonded diamond grains. Trapped interstitial regions preventexposure of the interstitial regions to a leaching agent, such as acid.Non-catalyst material and catalyst material is present in these trappedinterstitial regions. The non-catalyst material is distributedthroughout the polycrystalline diamond body and is present in adetectable amount throughout the polycrystalline diamond body. Thenon-catalyst material remains in the polycrystalline diamond body fromthe manufacturing process. The non-catalyst material results in anincrease in the leach rate of the PCD compact and in a reduction ofcatalyst material that is present in the trapped interstitial regions ofthe polycrystalline diamond body. The reduction of the catalyst materialin the trapped interstitial regions of the polycrystalline diamond bodyincreases the abrasion resistance of the PCD cutting element at elevatedtemperatures.

EXAMPLES Example 1 (Comparative)

A series of conventional cutting elements were made in a HPHT process.Each of the cutting elements was made according to the followingprocedure. Diamond particles having a D50 particle size of about 21 μmwere positioned in a refractory metal cup. The diamond particlesexhibited high purity and were free of contaminants. A cemented tungstencarbide substrate having about 10 wt. % cobalt (acting as the catalyst)and a planar interface was inserted into the refractory metal cup andpositioned proximate to the diamond particles. A reaction cell wasassembled in which the refractory metal cup, the diamond particles, andthe substrate were positioned inside a plurality of salt rings. Thereaction cell assembly was installed within a belt-type press in whichhigh pressure and high temperature were applied. The contents of thereaction cell were subjected to a maximum temperature of about 1500° C.and a maximum pressure of about 7 GPa. The contents of the reaction cellwere maintained above the temperature of cobalt for about 2 minutes. TheHPHT process produced a recovered polycrystalline body with good sinterquality.

The recovered polycrystalline body was processed to make a“double-pressed” cutting element. The recovered polycrystalline body wasseparated from the first substrate and machined to dimensional size bygrinding the outer diameter, the working surface of the polycrystallinediamond body, and the attachment surface opposite the working surface toform the polycrystalline diamond body. Following machining and prior toleaching of one illustrative polycrystalline diamond body, thepolycrystalline diamond body was evaluated by X-ray fluorescence anddetermined to contain about 9.09 wt. % cobalt along the side proximateto the substrate and about 9.61 wt. % cobalt along the side distal fromthe substrate. Further, the polycrystalline diamond body was determinedto have about 3.04 wt. % tungsten along the side proximate to thesubstrate and about 2.48 wt. % tungsten along the side distal from thesubstrate (in either elemental form or in solid solution as tungstencarbide).

The cutting element was introduced to a leaching agent that reacted withthe materials present in the interstitial regions of the cutting elementthat are positioned between diamond grains. The cutting element wasfully submerged in the leaching agent such that all of the exteriorsurfaces of the polycrystalline diamond body were introduced to theleaching agent.

The cutting element was periodically removed from the leaching agent,flushed of leaching agent to dilute the leaching agent, dried, weighted,and evaluated to determine the weight loss of the polycrystallinediamond body. The presented data is plotted in FIG. 6 and labeled as“Example 1.” Variation in the weight loss at various depicted timepoints may be attributed to normal variation in the manufacturingprocess.

The weight loss of the cutting elements subjected to the leachingprocess increased asymptotically towards a maximum value, at which pointthe polycrystalline diamond body was considered to be fully leached ofcatalyst material and non-catalyst material from the interstitialregions. The cutting elements according to the present example wereleached until there was a weight loss of about 10.5% was achieved. Theweight loss depicted in FIG. 6 with reference to Example 1 is indicativeof a conventional leaching rate profile.

Following leaching of the illustrative polycrystalline diamond body, thepolycrystalline diamond body was evaluated by X-ray fluorescence anddetermined to contain about 2.81 wt. % cobalt along the side proximateto the substrate and about 2.78 wt. % cobalt along the side distal fromthe substrate. Further, the polycrystalline diamond body was determinedto have about 0.835 wt. % tungsten along the side proximate to thesubstrate and about 0.819 wt. % tungsten along the side distal from thesubstrate (in either elemental form or in solid solution as tungstencarbide).

Example 2

Cutting elements according to the present disclosure were made accordingto the method described with respect to Example 1 above, however, priorto depositing the diamond particles in the refractory cup, the diamondparticles were mixed with 1.6 wt. % lead particles having a D50 of about20 μm. The reaction cell assembly that included the refractory cup, thediamond particles mixed with lead particles, and the substrate wassubjected to the HPHT process having the same maximum temperature andpressure as Example 1 and held at a temperature above the meltingtemperature of cobalt for the same duration as Example 1. The HPHTprocess produced a recovered polycrystalline body with good sinterquality.

The cutting element was introduced to a leaching agent that reacted withthe materials present in the interstitial regions of the cutting elementthat are positioned between diamond grains. The cutting element wasfully submerged in the leaching agent such that all of the exteriorsurfaces of the polycrystalline diamond body were introduced to theleaching agent.

The cutting element was periodically removed from the leaching agent,flushed of leaching agent to dilute the leaching agent, dried, weighted,and evaluated to determine the weight loss of the polycrystallinediamond body. The presented data is plotted in FIG. 6 and labeled as“Example 2.” Variation in the weight loss at various depicted timepoints may be attributed to normal variation in the manufacturingprocess.

The weight loss of the cutting elements subjected to the leachingprocess increased asymptotically towards a maximum value, at which pointthe polycrystalline diamond body was considered to be fully leached ofcatalyst material and non-catalyst material from the interstitialregions. The cutting elements according to the present example wereleached until there was a weight loss of about 11.8% was achieved.

As depicted in FIG. 6, the rate of removal of material during theleaching operation for cutting elements made according to Example 2exceeds the rate of removal of cutting elements made according toExample 1. For example, when extrapolated from the provided data, atevery time interval, the weight loss of cutting elements made accordingto Example 2 exceed the weight loss of cutting elements made accordingto Example 1. At 5 days, the extrapolated weigh loss of cutting elementsmade according to Example 2 exceeds the weight loss of cutting elementsmade according to Example 1 by about 60%; at 10 days, by about 50%; at15 days, by about 50%.

Example 3

Cutting elements according to the present disclosure were made accordingto the method described with respect to Example 1 above, however, priorto depositing the diamond particles in the refractory cup, the diamondparticles were mixed with 2.8 wt. % lead particles having a D50 of about20 μm. The reaction cell assembly that included the refractory cup, thediamond particles mixed with lead particles, and the substrate wassubjected to the HPHT process having the same maximum temperature andpressure as Example 1 and held at a temperature above the meltingtemperature of cobalt for the same duration as Example 1. The HPHTprocess produced a recovered polycrystalline body with good sinterquality.

Following machining and prior to leaching of one illustrativepolycrystalline diamond body, the polycrystalline diamond body wasevaluated by X-ray fluorescence and determined to contain about 9.31 wt.% cobalt along the side proximate to the substrate and about 8.84 wt. %cobalt along the side distal from the substrate. Further, thepolycrystalline diamond body was determined to have about 2.39 wt. %tungsten along the side proximate to the substrate and about 3.26 wt. %tungsten along the side distal from the substrate (in either elementalform or in solid solution as tungsten carbide).

The cutting element was introduced to a leaching agent that reacted withthe materials present in the interstitial regions of the cutting elementthat are positioned between diamond grains. The cutting element wasfully submerged in the leaching agent such that all of the exteriorsurfaces of the polycrystalline diamond body were introduced to theleaching agent.

The cutting element was periodically removed from the leaching agent,flushed of leaching agent to dilute the leaching agent, dried, weighted,and evaluated to determine the weight loss of the polycrystallinediamond body. The presented data is plotted in FIG. 6 and labeled as“Example 3.”

The weight loss of the cutting elements subjected to the leachingprocess increased asymptotically towards a maximum value, at which pointthe polycrystalline diamond body was considered to be fully leached ofcatalyst material and non-catalyst material from the interstitialregions. The cutting elements according to the present example wereleached until there was a weight loss of about 12.5% was achieved.

As depicted in FIG. 6, the rate of removal of material during theleaching operation for cutting elements made according to Example 3exceeds the rate of removal of cutting elements made according toExample 1. For example, when extrapolated from the provided data, atevery time interval, the weight loss of cutting elements made accordingto Example 3 exceed the weight loss of cutting elements made accordingto Example 1. At 5 days, the extrapolated weigh loss of cutting elementsmade according to Example 3 exceeds the weight loss of cutting elementsmade according to Example 1 by about 90%; at 10 days, by about 90%; at15 days, by about 65%.

Following leaching of the polycrystalline diamond body, thepolycrystalline diamond body was evaluated by X-ray fluorescence anddetermined to contain about 2.80 wt. % cobalt along the side proximateto the substrate and about 1.81 wt. % cobalt along the side distal fromthe substrate. Further, the polycrystalline diamond body was determinedto have about 0.784 wt. % tungsten along the side proximate to thesubstrate and about 0.458 wt. % tungsten along the side distal from thesubstrate (in either elemental form or in solid solution as tungstencarbide).

As illustrated by Examples 2 and 3 in comparison with Example 1, theintroduction of the non-catalyst material into the polycrystallinediamond body may accelerate the rate of material removal from thepolycrystalline diamond body.

Additionally, the introduction of non-catalyst material to thepolycrystalline diamond body may introduce a gradient of in the cobalt(i.e., catalyst material) and tungsten (i.e., additional non-catalystmaterial from the substrate), where the materials are at a higherconcentration at positions proximate to the substrate and at lowerconcentrations at positions distal from the substrate. In someembodiments, the rate of material removal may be accelerated in regionsof the polycrystalline diamond body having comparatively highconcentrations of non-catalyst material relative to catalyst material(i.e., at locations of relatively high lead concentration as compared tocobalt concentration).

It should now be understood that cutting elements and polycrystallinediamond bodies that are incorporated into cutting elements according tothe present disclosure may incorporate a non-catalyst material into theinterstitial regions between adjacent diamond grains. The non-catalystmaterial may have a higher rate of reaction than the catalyst materialwhen both are exposed to a leaching agent. Cutting elements andpolycrystalline diamond bodies incorporated into such cutting elementsmay exhibit increased leaching rates as compared to conventional cuttingelements, such that leaching rate of embodiments according to thepresent disclosure exceed a conventional leaching rate by at least about30%.

1. A method of forming a cutting element, comprising: assembling areaction cell comprising a plurality of diamond particles, anon-catalyst material, a catalyst material, and a substrate within arefractory metal container, wherein the non-catalyst material isgenerally immiscible in the catalyst material when both are held at thegreater of the melting or liquidus temperature of the catalyst materialor the non-catalyst material; subjecting the reaction cell and itscontents to a high pressure high temperature sintering process in whichthe catalyst material promotes formation of inter-diamond bondingbetween adjacent diamond particles to form a poly crystalline diamondbody that is attached to the substrate; contacting at least a portion ofthe polycrystalline diamond body with a leaching agent to removecatalyst material and non-catalyst material from the diamond body, aconventional leaching profile comprising time measured along a firstaxis and a corresponding weight loss percentage presented along a secondaxis; and wherein a leaching rate at which the catalyst material and thenon-catalyst material are leached from the diamond body exceeds aconventional leaching rate profile by at least about 30%.
 2. The methodof claim 1, wherein the leaching rate of the catalyst material and thenon-catalyst material exceeds the convention leaching rate profile by atleast about 40%.
 3. The method of claim 1, wherein the leaching rate ofthe catalyst material and the non-catalyst material exceeds theconvention leaching rate profile by up to about 60%.
 4. The method ofclaim 1, wherein a leached depth of 800 μιη from the working surface ofthe polycrystalline diamond body is achieved in less than about 7 daysof exposure to the leaching agent.
 5. The method of claim 4, wherein aleached depth of 800 μιη from the working surface of a polycrystallinediamond body according to the conventional leaching rate profile isachieved in about 10 days of exposure to the leaching agent.
 6. Themethod according to claim 1, wherein the non-catalyst material has alower liquidus or melting temperature than the liquidus or meltingtemperature of the catalyst material.
 7. The method according to claim1, wherein the non-catalyst material has a higher rate of reaction withthe leaching agent than the catalyst material.
 8. The method of claim 1,wherein high pressure high temperature sintering process includes:melting the non-catalyst material and pushing the melted non-catalystmaterial through at least a portion of the plurality of diamondparticles, thereby surrounding at least a portion of the plurality ofindividual diamond particles; and melting the catalyst material andpushing the melted catalyst material through at least a portion of theplurality of diamond particles and displacing a portion of thenon-catalyst material from interstitial regions between the individualdiamond grains.
 9. The method of claim 1, wherein the non-catalystmaterial is mixed with the diamond particles prior to being assembled inthe reaction cell.
 10. The method of claim 1, wherein the catalystmaterial is incorporated into the substrate.
 11. The method of claim 1,wherein the catalyst material is positioned in a catalyst source that isseparate from the substrate.
 12. The method of claim 1, furthercomprising the selecting of a multimodal feed that comprises a firstpopulation of diamond particles having a first particle sizedistribution function and a second population of diamond particleshaving a second particle size distribution function.
 13. The method ofclaim 12, wherein the multimodal feed further comprises a thirdpopulation of diamond particles having a third particle sizedistribution function.
 14. The method of claim 1, wherein the diamondbody comprises a first portion positioned proximate to the substrate andhaving a first particle size distribution function and a second portionpositioned distally from the substrate and having a second particle sizedistribution function.
 15. The method of claim 14, wherein the firstportion has a median particle size that is smaller than a medianparticle size of the second portion.
 16. The method of claim 14, whereinthe first portion has a median particle size that is larger than amedian particle size of the second portion.
 17. The method of claim 1,wherein the diamond body further comprises metal carbide, and a metalcarbide concentration within the diamond body is less than about 70% ofa conventional metal carbide concentration.
 18. The method of claim 1,wherein the non-catalyst material is lead or alloys thereof.
 19. Themethod of claim 1, wherein the non-catalyst material is bismuth oralloys thereof.
 20. The method of claim 1, wherein the non-catalystmaterial is positioned between the diamond particles and the substrate.21. A cutting element, comprising: a substrate comprising a metalcarbide and a catalyst material; and a poly crystalline diamond bodybonded to the substrate, the poly crystalline diamond body comprising aplurality of diamond grains bonded to adjacent diamond grains indiamond-to-diamond bonds and a plurality of interstitial regionspositioned between adjacent diamond grains, the plurality ofinterstitial regions comprising an immiscible non-catalyst material, thecatalyst material, the metal carbide, or combinations thereof, wherein ametal carbide concentration within the diamond body is less than about70% of a conventional metal carbide concentration.
 22. The cuttingelement of claim 21, wherein the metal carbide comprises cementedtungsten carbide.
 23. The cutting element of claim 21, wherein thenon-catalyst material has a lower liquidus or melting temperature thanthe liquidus or melting temperature of the catalyst material.
 24. Thecutting element of claim 21, wherein the diamond particles comprise amultimodal population of bonded diamond grains that comprises a firstpopulation of diamond particles having a first particle sizedistribution function and a second population of diamond particleshaving a second particle size distribution function.
 25. The cuttingelement of claim 24, wherein the multimodal population of bonded diamondgrains further comprises a third population of diamond particles havinga third particle size distribution function.
 26. The cutting element ofclaim 21, wherein the poly crystalline diamond body comprises a firstportion positioned proximate to the substrate and having a firstparticle size distribution function and a second portion positioneddistally from the substrate and having a second particle sizedistribution function.
 27. The cutting element of claim 26, wherein thefirst portion has a median particle size that is smaller than a medianparticle size of the second portion.
 28. The cutting element of claim26, wherein the first portion has a median particle size that is largerthan a median particle size of the second portion.
 29. A drill bit,comprising: a bit body comprising a leading end structure for drilling asubterranean formation; and a plurality of cutting elements mounted tothe blades, at least one of the plurality of cutting elementscomprising: a substrate comprising a metal carbide and a catalystmaterial; and a polycrystalline diamond body bonded to the substrate,the polycrystalline diamond body comprising a plurality of diamondgrains bonded to adjacent diamond grains in diamond-to-diamond bonds,the polycrystalline diamond body further comprising a plurality ofinterstitial regions positioned between adjacent diamond grains, theplurality of interstitial regions comprising an immiscible non-catalystmaterial, catalyst material, metal carbide, or combinations thereof,wherein a metal carbide concentration within the diamond body is lessthan about 70% of a conventional metal carbide concentration.
 30. Amethod of forming a cutting element, comprising: assembling a reactioncell comprising a plurality of diamond particles, a non-catalystmaterial, a catalyst material, and a substrate within a refractory metalcontainer, wherein the non-catalyst material is generally immiscible inthe catalyst material when both are held at the greater of the meltingor liquidus temperature of the catalyst material or the non-catalystmaterial; subjecting the reaction cell and its contents to a highpressure high temperature sintering process in which the catalystmaterial promotes formation of inter-diamond bonding between adjacentdiamond particles to form a poly crystalline diamond body that isattached to the substrate; contacting at least a portion of thepolycrystalline diamond body with a leaching agent to remove catalystmaterial and non-catalyst material from the diamond body, wherein thenon-catalyst material has a higher rate of reaction with the leachingagent than the catalyst material.
 31. The method of claim 30, whereinthe non-catalyst material has a lower liquidus or melting temperaturethan the liquidus or melting temperature of the catalyst material. 32.The method of claim 30, wherein a leached depth of 800 μιη from theworking surface of the diamond body is achieved in less than about 7days of exposure to the leaching agent.
 33. The method of claim 30,wherein the diamond body has a non-zero non-catalyst materialconcentration that increases from the substrate to the working surface,wherein when leaching agent is contacted to the working surface, areaction rate of the leaching reaction decreases with increasingdistance from the working surface.